2-mercaptobenzimidazole films formed at ultra-low pressure on copper: adsorption, thermal stability and corrosion inhibition performance

2-mercaptobenzimidazole (2-MBI) is considered as an effective corrosion inhibitor for copper. In this study, the adsorption of 2-MBI on pristine and pre-oxidized Cu(111) surfaces was investigated by sublimation at ultra low pressure, using Auger Electron Spectroscopy, Scanning Tunneling Microscopy and X-ray Photoelectron Spectroscopy in order to understand its corrosion inhibition properties. 2-MBI adsorbs with S and N atoms bonded to Cu. On pristine Cu(111) surface, a self-assembled monolayer is formed at about 5 L, with the adsorption of atomic S resulting from molecule decomposition to form a (sqrt(7)xsqrt(7))R19.1° structure, and that of the molecule forming a (8x8) structure. 2-MBI is lying flat in the adsorbed multilayer. Oxidation of copper prior to exposure results in compact and homogeneous molecular films, with dissociation and substitution of 2D oxide by 2-MBI, but much more slower than that for 2-mercaptobenzothiazole (2-MBT). A multilayer of 2-MBI can block the initial stages of oxidation of copper under low oxygen pressure at room temperature, and the molecular layer is stable until 500°C. The comparison with 2-MBT suggests that the latter is a better corrosion inhibitor for copper at room temperature.